The present invention relates to an interconnection construction and a process for its application for both electrically connecting and thermally insulating adjacent electrical devices.
Many electrical assemblies require that two or more elements be both electrically connected and thermally insulated, one from the other, to prevent heat generated in one portion from being transmitted to another electrically connected portion, or vice-versa. For example, one portion may be heat sensitive, where its operation is temperature dependent, that is, a change in its temperature will adversely affect its operation. A specific example is a pyroelectric detector whose signals are coupled electrically to a readout circuit for processing the signals. A typical construction comprises a pyroelectric detector focal plane array hybrid which is mounted on an integrated circuit and which generates heat to comprise a large thermal mass. Because the signal generated by a pyroelectric detector is proportional to its time rate of temperature change, any heat transmitted thereto will degrade the detector signal.
It has been conventional practice to cool infrared detectors, such as by cryogenic means. While such cooling is effective, it adds apparatus, weight, and cost to and servicing of the entire electronic assembly. Where the need is to economize on weight, space and cost, other alternatives must be sought. The operation of a pyroelectric solid state array detector without cooling has particular importance in thermal imaging sights.
Present systems, using a photoconductive mercury-cadmium-teluride as the detector, employs either a sterling compressor or a JT crystal with bottle for cooling the detector to 77.degree. K, which weighs approximately 5 pounds and, in the compressor, greater than 20 watts of power is required. Other requirements for transportable systems, weighing approximately 5 pounds, are being considered to obtain thermo-electric cooling to 185.degree. K for operation at 300.degree. K with the weight of 5 to 6 pounds, to enable the systems to be carried by an individual.
Thus, conventional thermal imaging systems which need to be transportable, such as for battlefield uses or fire prevention, are expensive, bulky, and their photoconductive detectors require cryogenic cooling. These imaging systems, therefore, must be permanently installed on a large vehicle, such as a tank or an aircraft. They are difficult to maintain in the field, and create large logistical problems because their cooling bottles containing liquid nitrogen must be frequently replaced. Despite, these drawbacks, thermal imaging systems have proven to be excellent surveillance sensors and have the added advantage of being able to provide night vision by means of passive detection. Having staring pyroelectric systems, which do not need cooling or scanning, will eliminate most of the complexity and cost while retaining their performance, i.e., in resolution and sensitivity. Therefore, it is very desirable to have systems employing uncooled pyroelectric detector arrays.